Add ability to signal and perform online volume size change

Allow Cinder to use external events to signal a volume extension.

1) Nova will then call os-brick to perform the volume extension
   so the host can detect its new size.
2) Compute driver will resize the device in QEMU so instance can detect
   the new disk size without rebooting.

This change:

* Adds the 'volume-extended' external event.
  The event tag needs to be the extended volume id.
* Bumps the latest microversion to 2.51.
* Exposes non-traceback instance action event details for
  non-admins on the microversion. This is needed for the
  non-admin API user that initiated the volume extend
  operation to be able to tell when the nova-compute side
  is complete.

Co-Authored-By: Matt Riedemann <mriedem.os@gmail.com>

Blueprint: nova-support-attached-volume-extend

Change-Id: If10cffd0dc4c9879f6754ce39bee5fae1d04f474

1 files changed, 13 insertions, 0 deletions

diff --git a/nova/virt/driver.py b/nova/virt/driver.py
index c043404202..87cb782eff 100644
--- a/nova/virt/driver.py
+++ b/nova/virt/driver.py
@@ -129,6 +129,7 @@ class ComputeDriver(object):
         "supports_device_tagging": False,
         "supports_tagged_attach_interface": False,
         "supports_tagged_attach_volume": False,
+        "supports_extend_volume": False,
     }
 
     def __init__(self, virtapi):
@@ -478,6 +479,18 @@ class ComputeDriver(object):
         """
         raise NotImplementedError()
 
+    def extend_volume(self, connection_info, instance):
+        """Extend the disk attached to the instance.
+
+        :param dict connection_info:
+            The connection for the extended volume.
+        :param nova.objects.instance.Instance instance:
+            The instance whose volume gets extended.
+
+        :return: None
+        """
+        raise NotImplementedError()
+
     def attach_interface(self, context, instance, image_meta, vif):
         """Use hotplug to add a network interface to a running instance.